scholarly journals Actin Bundles in The Pollen Tube

2018 ◽  
Vol 19 (12) ◽  
pp. 3710 ◽  
Author(s):  
Shujuan Zhang ◽  
Chunbo Wang ◽  
Min Xie ◽  
Jinyu Liu ◽  
Zhe Kong ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Tip Growth ◽  
Imaging Techniques ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Growth Strategy ◽  
Regulation Mechanism ◽  
Actin Bundles ◽  
Angiosperm Pollen ◽  
Plant Pollen

The angiosperm pollen tube delivers two sperm cells into the embryo sac through a unique growth strategy, named tip growth, to accomplish fertilization. A great deal of experiments have demonstrated that actin bundles play a pivotal role in pollen tube tip growth. There are two distinct actin bundle populations in pollen tubes: the long, rather thick actin bundles in the shank and the short, highly dynamic bundles near the apex. With the development of imaging techniques over the last decade, great breakthroughs have been made in understanding the function of actin bundles in pollen tubes, especially short subapical actin bundles. Here, we tried to draw an overall picture of the architecture, functions and underlying regulation mechanism of actin bundles in plant pollen tubes.

scholarly journals Protein Analysis of Pollen Tubes after the Treatments of Membrane Trafficking Inhibitors Gains Insights on Molecular Mechanism Underlying Pollen Tube Polar Growth

2021 ◽  
Vol 40 (2) ◽  
pp. 205-222
Author(s):  
Monica Scali ◽  
Alessandra Moscatelli ◽  
Luca Bini ◽  
Elisabetta Onelli ◽  
Rita Vignani ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Actin Cytoskeleton ◽  
Membrane Trafficking ◽  
Tip Growth ◽  
Male Gametophyte ◽  
Pollen Tubes ◽  
Structural Features ◽  
Two Dimensional Gel Electrophoresis ◽  
Depth Analysis

AbstractPollen tube elongation is characterized by a highly-polarized tip growth process dependent on an efficient vesicular transport system and largely mobilized by actin cytoskeleton. Pollen tubes are an ideal model system to study exocytosis, endocytosis, membrane recycling, and signaling network coordinating cellular processes, structural organization and vesicular trafficking activities required for tip growth. Proteomic analysis was applied to identifyNicotiana tabacumDifferentially Abundant Proteins (DAPs) after in vitro pollen tube treatment with membrane trafficking inhibitors Brefeldin A, Ikarugamycin and Wortmannin. Among roughly 360 proteins separated in two-dimensional gel electrophoresis, a total of 40 spots visibly changing between treated and control samples were identified by MALDI-TOF MS and LC–ESI–MS/MS analysis. The identified proteins were classified according to biological processes, and most proteins were related to pollen tube energy metabolism, including ammino acid synthesis and lipid metabolism, structural features of pollen tube growth as well modification and actin cytoskeleton organization, stress response, and protein degradation. In-depth analysis of proteins corresponding to energy-related pathways revealed the male gametophyte to be a reliable model of energy reservoir and dynamics.

Overgrowth of Pollen Tubes in Embryo Sacs of Rhododendron Following Interspecific Pollinations

1986 ◽  
Vol 34 (4) ◽  
pp. 413 ◽  
Author(s):  
EG Williams ◽  
V Kaul ◽  
JL Rouse ◽  
BF Palser
Keyword(s):  
Pollen Tube ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Egg Cell ◽  
Interspecific Crosses ◽  
Main Body

Frequent overgrowths of pollen tubes within the embryo sac are characteristic of a number of interspecific crosses in the genus Rhododendron (Ericaceae). The combined techniques of sectioning, squashing and whole-ovule clearing have confirmed that in ovules showing this phenomenon the pollen tube fails to terminate growth and release sperms on entry into a synergid; instead it continues to grow beyond the synergid and egg cell, often filling the main body of the embryo sac with a coiled and distorted mass. Such ovules fail to develop further. The occurrence and possible causes of this error syndrome are discussed.

Ultrastructural Aspects of the Self-Incompatibility Mechanism in Lycopersicum Peruvianum Mill

1973 ◽  
Vol 12 (2) ◽  
pp. 403-419 ◽  
Author(s):  
D. DE NETTANCOURT ◽  
M. DEVREUX ◽  
A. BOZZINI ◽  
M. CRESTI ◽  
E. PACINI ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Tube Wall ◽  
Degradation Mechanism ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
Self Incompatibility ◽  
Weak Reaction ◽  
General Hypothesis ◽  
Incompatible Pollen ◽  
Compatible Pollen

The experimental results obtained show that the tip of the incompatible pollen tube bursts open after the outer-wall has considerably expanded in the intercellular spaces of the conducting tissue and the inner-wall has disappeared and numerous particles have accumulated in the tube cytoplasm. These particles, which measure approximately 0.2 µm in diameter and give a weak reaction to the test of Thiéry, differ in many respects from the vesicles normally present in compatible pollen tubes growing through the style; they appear to resemble, in some cases, the spheres which are discharged by the compatible pollen tubes after they have reached the embryo-sac. It is considered that these observations support the current belief that the tube wall is the site of action for the incompatibility proteins and suggest that self-incompatibility is not a passive process resulting from lack of growth stimulation but an active event which leads to the destruction of the incompatible pollen tubes. The degradation mechanism involved appears similar to the one which enables the compatible pollen tube to release its contents in the degenerated synergid and presents some analogies with the lytic process taking place in virus-infected cells. The general hypothesis is presented that the particles observed in the cytoplasm of self-incompatible pollen tubes consist of a mixture of incompatibility proteins and of basic constituents of the tube wall.

scholarly journals Signaling in Pollen Tube Growth: Beyond the Tip of the Polarity Iceberg

Plants ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 156 ◽  
Author(s):  
Nolan Scheible ◽  
Andrew McCubbin
Keyword(s):  
Pollen Tube ◽  
Signaling Pathways ◽  
Pollen Tube Growth ◽  
Tip Growth ◽  
Holistic Approach ◽  
Pollen Tubes ◽  
Small Gtpase ◽  
Tube Growth ◽  
Concerted Action ◽  
Current State

The coordinated growth of pollen tubes through floral tissues to deliver the sperm cells to the egg and facilitate fertilization is a highly regulated process critical to the Angiosperm life cycle. Studies suggest that the concerted action of a variety of signaling pathways underlies the rapid polarized tip growth exhibited by pollen tubes. Ca2+ and small GTPase-mediated pathways have emerged as major players in the regulation of pollen tube growth. Evidence suggests that these two signaling pathways not only integrate with one another but also with a variety of other important signaling events. As we continue to elucidate the mechanisms involved in pollen tube growth, there is a growing importance in taking a holistic approach to studying these pathways in order to truly understand how tip growth in pollen tubes is orchestrated and maintained. This review considers our current state of knowledge of Ca2+-mediated and GTPase signaling pathways in pollen tubes, how they may intersect with one another, and other signaling pathways involved. There will be a particular focus on recent reports that have extended our understanding in these areas.

Pollination Sub-Systems Distinguished by Pollen Tube Arrest after Incompatible Interspecific Crosses in Rhododendron (Ericaceae)

1982 ◽  
Vol 53 (1) ◽  
pp. 255-277
Author(s):  
ELIZABETH G. WILLIAMS ◽  
BRUCE R. KNOX ◽  
JOHN L. ROUSE
Keyword(s):  
Pollen Tube ◽  
Tip Growth ◽  
Interspecific Cross ◽  
Embryo Sac ◽  
Epifluorescence Microscopy ◽  
Interspecific Crosses ◽  
Abnormal Behaviour ◽  
Callose Deposition ◽  
Variable Diameter ◽  
Stigmatic Exudate

The cytology of compatible and interspecific incompatible pollinations has been followed in selected species of the genus Rhododendron (Ericaceae). Pollinated pistils were fixed, cleared, stained in decolourized aniline blue, and observed by epifluorescence microscopy. Ten different abnormalities of arrested pollen tube tips have been detected, including burst, tapered, swollen, coiled, spiralling, spiky and variable diameter syndromes. A series of five errors of callose deposition in incompatible tubes has also been defined. Six different regions in the pistil for expression of pollen tube arrest have been found, including the stigmatic exudate, the mucilage of the upper and lower style canal, the ovary loculus, the micropyle. There may also be abnormal behaviour after entry into the embryo sac. Both the site of pollen tube arrest within the pistil, and the error syndrome of tip growth and callose deposition anomalies, are characteristic of each interspecific cross. These results are discussed in relation to the genetic control of reproduction.

scholarly journals Accelerated sliding of pollen tube organelles along Characeae actin bundles regulated by Ca2+.

1988 ◽  
Vol 106 (5) ◽  
pp. 1539-1543 ◽  
Author(s):  
T Kohno ◽  
T Shimmen
Keyword(s):  
Heat Treatment ◽  
Pollen Tube ◽  
Cytoplasmic Streaming ◽  
Pollen Tubes ◽  
The Other ◽  
Cell Models ◽  
Organelle Movement ◽  
Actin Bundles ◽  
Other Hand ◽  
Order Of Magnitude

Pollen tubes show active cytoplasmic streaming. We isolated organelles from pollen tubes and tested their ability to slide along actin bundles in characean cell models. Here, we show that sliding of organelles was ATP-dependent and that motility was lost after N-ethylmaleimide or heat treatment of organelles. On the other hand, cytoplasmic streaming in pollen tube was inhibited by either N-ethylmaleimide or heat treatment. These results strongly indicate that cytoplasmic streaming in pollen tubes is supported by the "actomyosin"-ATP system. The velocity of organelle movement along characean actin bundles was much higher than that of the native streaming in pollen tubes. We suggested that pollen tube "myosin" has a capacity to move at a velocity of the same order of magnitude as that of characean myosin. Moreover, the motility was high at Ca2+ concentrations lower than 0.18 microM (pCa 6.8) but was inhibited at concentration higher than 4.5 microM (pCa 5.4). In conclusion, cytoplasmic streaming in pollen tubes is suggested to be regulated by Ca2+ through "myosin" inactivation.

scholarly journals pH gradients are not associated with tip growth in pollen tubes of Lilium longiflorum

1997 ◽  
Vol 110 (15) ◽  
pp. 1729-1740 ◽  
Author(s):  
M.D. Fricker ◽  
N.S. White ◽  
G. Obermeyer
Keyword(s):  
Pollen Tube ◽  
Tip Growth ◽  
Lilium Longiflorum ◽  
Pollen Tubes ◽  
Tube Growth ◽  
Cytoplasmic Ph ◽  
Clear Zone ◽  
External Application ◽  
Ph Gradients ◽  
External Ph

The cytoplasmic pH of growing pollen tubes of Lilium longiflorum Thunb. was measured using the pH-sensitive fluorescent dye 2′,7′-bis-(carboxyethyl)-5(6′)-carboxyfl uorescein and confocal fluorescence ratio imaging. The average cytoplasmic pH in the clear zone of the pollen tube tip was pH 7.11, and no consistent pH gradients were detected in the clear zone, averaging around -1.00 milli pH unit microm(−1), or along the first 50 microm of the tube (3.62 milli pH units microm[-1]). In addition, no correlation was observed between the absolute tip cytoplasmic pH or the pH gradient and the pollen tube growth rates. Shifts of external pH to more acidic pH values (pH 4.5) caused a relatively small acidification by 0.18 pH units, whereas a more alkaline external pH >7.0 caused a dramatic increase in cytoplasmic pH and growth stopped immediately. Stimulation of the plasma membrane H+-ATPase by fusicoccin, resulted in an increase of tube growth but no change in cytoplasmic pH. On the other hand, vanadate (250–500 microM), a putative inhibitor of the pump, stopped tube growth and a slight cytoplasmic alkalinisation of 0.1 pH units was observed. Vanadate also arrested fusicoccin-stimulated growth and stimulated an increased alkalinisation of around 0.2 pH units. External application of CaCl2 (10 mM) caused a small acidification of less than 0.1 pH units in the clear zone, whilst LaCl3 (250 microM) caused slight and rather variable perturbations in cytoplasmic pH of no more than 0.1 pH units. Both treatments stopped growth. It was inferred from these data that tip-acid cytoplasmic pH gradients do not play a central role in the organisation or maintenance of pollen tube tip growth.

Floral Anatomy and Pollen Tube Growth in the Quandong (Santalum acuminatum (R. Br.) A. DC.)

1982 ◽  
Vol 30 (6) ◽  
pp. 601 ◽  
Author(s):  
M Sedgley
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Floral Anatomy ◽  
Embryo Sac ◽  
Pollen Tubes ◽  
The Other ◽  
Tube Growth ◽  
Scanning Electron

Floral anatomy and pollen tube growth in the quandong were studied using light and scanning electron microscopy. The flowers had four perianth lobes and four stamens whose anthers dehisced by longitudinal slits. The pollen became caught in long unicellular hairs adjacent to the anthers. The central disc secreted nectar through raised stomata. The stigma papilla cells had a cuticle with a rough surface overlying thick PAS-positive walls. The half-inferior ovary normally contained two ovules. The embryo sac extended beyond the ovule at the micropylar end and into the placenta at the chalazal end. Half of the ovaries observed at both anthesis and 4 days following anthesis had no embryo sacs and the other half had one embryo sac. Occasional ovaries had two embryo sacs and some underdeveloped embryo sacs were observed that did not extend beyond the ovule or into the placenta. Pollen tubes had reached the ovary by 1 day following pollination and the stigma was receptive for 8 days following anthesis. Only half of the pistils had pollen tubes in the ovary. Unpollinated flowers had no pollen tube growth in the pistil.

scholarly journals Coordinated Localization and Antagonistic Function of NtPLC3 and PI4P 5-Kinases in the Subapical Plasma Membrane of Tobacco Pollen Tubes

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 452 ◽  
Author(s):  
Irene Stenzel ◽  
Till Ischebeck ◽  
Linh Hai Vu-Becker ◽  
Mara Riechmann ◽  
Praveen Krishnamoorthy ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Pollen Tube ◽  
Tip Growth ◽  
Pollen Tubes ◽  
Dominant Negative ◽  
Membrane Domains ◽  
Tobacco Pollen ◽  
Polar Tip Growth ◽  
Spinning Disc

Polar tip growth of pollen tubes is regulated by the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2), which localizes in a well-defined region of the subapical plasma membrane. How the PtdIns(4,5)P2 region is maintained is currently unclear. In principle, the formation of PtdIns(4,5)P2 by PI4P 5-kinases can be counteracted by phospholipase C (PLC), which hydrolyzes PtdIns(4,5)P2. Here, we show that fluorescence-tagged tobacco NtPLC3 displays a subapical plasma membrane distribution which frames that of fluorescence-tagged PI4P 5-kinases, suggesting that NtPLC3 may modulate PtdIns(4,5)P2-mediated processes in pollen tubes. The expression of a dominant negative NtPLC3 variant resulted in pollen tube tip swelling, consistent with a delimiting effect on PtdIns(4,5)P2 production. When pollen tube morphologies were assessed as a quantitative read-out for PtdIns(4,5)P2 function, NtPLC3 reverted the effects of a coexpressed PI4P 5-kinase, demonstrating that NtPLC3-mediated breakdown of PtdIns(4,5)P2 antagonizes the effects of PtdIns(4,5)P2 overproduction in vivo. When analyzed by spinning disc microscopy, fluorescence-tagged NtPLC3 displayed discontinuous membrane distribution omitting punctate areas of the membrane, suggesting that NtPLC3 is involved in the spatial restriction of plasma membrane domains also at the nanodomain scale. Together, the data indicate that NtPLC3 may contribute to the spatial restriction of PtdIns(4,5)P2 in the subapical plasma membrane of pollen tubes.

scholarly journals Arabidopsis ABCG28 is required for the apical accumulation of reactive oxygen species in growing pollen tubes

2019 ◽  
Vol 116 (25) ◽  
pp. 12540-12549 ◽  
Author(s):  
Thanh Ha Thi Do ◽  
Hyunju Choi ◽  
Michael Palmgren ◽  
Enrico Martinoia ◽  
Jae-Ung Hwang ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Tip Growth ◽  
Ectopic Expression ◽  
Reactive Oxygen ◽  
Pollen Tubes ◽  
Tube Growth ◽  
Oxygen Species ◽  
Ros Accumulation

Tip-focused accumulation of reactive oxygen species (ROS) is tightly associated with pollen tube growth and is thus critical for fertilization. However, it is unclear how tip-growing cells establish such specific ROS localization. Polyamines have been proposed to function in tip growth as precursors of the ROS, hydrogen peroxide. The ABC transporter AtABCG28 may regulate ROS status, as it contains multiple cysteine residues, a characteristic of proteins involved in ROS homeostasis. In this study, we found that AtABCG28 was specifically expressed in the mature pollen grains and pollen tubes. AtABCG28 was localized to secretory vesicles inside the pollen tube that moved toward and fused with the plasma membrane of the pollen tube tip. Knocking out AtABCG28 resulted in defective pollen tube growth, failure to localize polyamine and ROS to the growing pollen tube tip, and complete male sterility, whereas ectopic expression of this gene in root hair could recover ROS accumulation at the tip and improved the growth under high-pH conditions, which normally prevent ROS accumulation and tip growth. Together, these data suggest that AtABCG28 is critical for localizing polyamine and ROS at the growing tip. In addition, this function of AtABCG28 is likely to protect the pollen tube from the cytotoxicity of polyamine and contribute to the delivery of polyamine to the growing tip for incorporation into the expanding cell wall.

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